The Coast Line
Between Exmouth in Devon and Old Harry Rocks, Swanage in Dorset can be found one of the most complete sequences through the Triassic, Jurassic and Cretaceous periods of geological time anywhere in the world. The reason for this is simple, the overall dip of the rocks is gently to the east and this brings successively younger rocks to sea level along the coast with the oldest in the west and the youngest to the east.
The cliffs of West Dorset are formed from rocks of Lower Jurassic age and are capped by younger sandstone of Cretaceous age that give Golden Cap its cap.
Lyme Regis lies at the point where the Triassic rocks disappear below the sea and the oldest Jurassic rocks, thick clays and thin limestone of the 'Lias', form the cliffs. These rocks were deposited in a moderately deep tropical sea that was packed with marine life and as a result fossils are very common. Some, such as pencil shaped belemnites and coiled ammonites, are easy to find but others, like ichthyosaurs (marine reptiles) and fish are far rarer. The rocks also contain evidence of life on the land in the form of fossil wood, insects and even dinosaurs that were washed into the sea some 200 million years ago.